1. Field of the Invention
The present invention relates generally to a reflective type screen preferably employable for a projector such as a video projector or the like. More particularly, the present invention relates to a reflective type screen which assures that an enlarged image projected under a bright visual circumstance can clearly be displayed with a high optical contrast.
2. Description of the Related Art
To facilitate understanding of the present invention, a conventional reflective type screen will be described below with reference to FIG. 8 and FIG. 9. First, referring to FIG. 8, the reflective type screen 1 preferably employable for a projector includes a reflective surface layer 3 usually molded of a white polyvinyl cellulose film, and the reflective surface layer 3 is laid on the upper surface of a substrate 2. The surface of the reflective surface layer 3 is subjected to diffusion processing and then coated with a certain agent effective for preventing the reflective surface layer 3 from being undesirably contaminated with foreign materials. When the screen 1 is practically used, an image is projected on the screen 1 in a dark room without any invasion of exterior light into the dark room.
With respect to the conventional reflective type screen having a white polyvinyl cellulose film used therefor as mentioned above, any image should be projected on the screen in the dark room. In view of this fact, in recent years, a trial has been made so as to enable a projected image to be visually observed by viewers in a light room, as disclosed in an official gazette of, e.g., Japanese Unexamined Publication Patent (Kokai) NO. 62-266980. According to the prior invention, a light irradiated from a projector is projected onto the screen through a polarizing filter. The screen includes a polarizing plate having a permeation axis extending in the same polarization direction as that of the polarizing filter. In addition, the screen includes a reflective surface so as to allow the reflected light to be reflected therefrom while maintaining the same polarized state as that of an incident light. The arrangement of the polarizing plate and the reflective surface in the above-described manner makes it possible that reflection of an exterior light is substantially suppressed over the surface of the screen so that the exterior light reflected from the surface of the screen is not visually recognized by the viewers.
Additionally, referring to FIG. 9, the reflective type screen 1 is constructed in a laminated structure and includes a polarizing plate layer 40 and a stereo screen 41 as seen from the incident side wherein an incident light is irradiated in the A arrow-marked direction in the drawing. Both the layers 40 and 41 are adhesively secured to each other to form an integral structure.
It has been required from the viewpoint of a role of the reflective type screen that a light irradiated from the projector is expansively diffused with a wide angle (predetermined angle) so that an image on the screen can be observed by many viewers with uniform brightness. To meet the requirement, the surface of the screen should be prepared in the form of a diffusion surface.
However, since the conventional reflective type screen is constructed such that a reflective surface layer is arranged on the rear surface of a polarizing plate layer and both the layers are prepared in the form of a flat and smooth surface, an incident light is reflected from the flat and smooth surfaces as if it is reflected from a mirror surface. Thus, there arises a problem that an image on the screen can not properly be observed by a part of the viewers (who stay on both the sides as seen from the screen) because the incident light is not expansively diffused with a wide angle.